(1) Field of the Invention
The invention relates in general to filtering and in particular to a filter device for filtering a suspension and a method for filtering a suspension in a filter device.
(2) Description of Related Art including information disclosed under 37 CFR 1.97 and 1.98
In a known configuration, a press filter device comprises a stationary head piece, a movable end piece, and a pack of recess plates disposed between the head piece and the end piece. A filter chamber is formed between adjacent recess plates by a recess of at least one of a pair of adjacent recess plates. The filter device further comprises a suspension pipe for introducing suspension into the filter chambers of the device, wherein the suspension pipe runs from the head piece to the end piece through the pack. Moreover, the filter device is provided with a supply pipe communicating with the end piece and providing a suspension stream to the suspension pipe. In the known filter devices, the supply pipes to the end piece are flexible hoses or pipes with elbow joints, running parallel to the pack. When opening and closing the pack, one end of the supply pipe moves together with the end piece, whereas the other end remains connected to a fixed suspension source. A flexible supply pipe allows movements of the end piece, but the flexible supply pipe needs to be stiff enough for piping a high-pressure suspension from the suspension source to the end piece. This high stiffness of the supply pipe always causes a torsional moment when moving the end piece.
Furthermore, flexible supply pipes increase the risk of leakage of the known filter devices. Due to safety reasons, use of the known filter devices is thus deprecated for filtering hazardous suspensions.
Furthermore in some filter devices, the suspension pipe runs through the pack outside the filter chamber, causing excentric pressure load of up to several tons to the end piece during the filtration cycle. Stiffness of the supply pipe and pressure load from the suspension pipe easily cause misalignment and deflection of the end piece, and of the recess plates of the pack.